The present invention relates to under bridge access apparatus and, more particularly, to an under bridge access apparatus having a cross-linking member connecting together a tower with a vehicular chassis.
An xe2x80x9cunder bridge access apparatusxe2x80x9d commonly comprises a hydraulically-operated mechanism mounted onto a vehicular chassis, such as that of a truck or trailer. The mechanism is hydraulically foldable into a compactly retracted storage/transport position and hydraulically extendable, when situated on a bridge or similar structure, to extend over and down from a bridge railing and then under the bridge to provide a platform on which workers can stand while performing maintenance, repair and like operations.
Various conventional under bridge access apparatus are well-known and, for example, include those disclosed by U.S. Pat. Nos. 2,669,490; 3,085,648; 3,262,517; 3,357,517; 3,456,756; 3,608,669; 3,774,719; 4,074,790; 4,154,318; 4,461,369; 4,556,124; 4,624,340; 4,633,975; 4,646,875; 4,690,247; 4,893,696; 4,696,371; 5,253,731; 5,318,149; and 5,435,410.
A particular conventional under bridge access apparatus sold by Hydra Platforms MFG., Inc., of Charlotte, N.C., as Model HPT-15/50 has met with commercial success. This apparatus includes a tower and vehicular chassis. The chassis includes a rotatable base mounted thereon and a tiltable frame pivotally mounted to the base. A catwalk extends between and rigidly connects the tiltable frame to the tower. The tower itself includes a ladder section and a platform section pivotally and rotatably mounted to the ladder section. The tower, originally aligned with and carried over the vehicular chassis, is positioned into a vertical position adjacent a bridge by rotating the base and pivoting the tiltable frame approximately ninety degrees. A drawback to this particular under bridge access apparatus is that the tower is fixed relative to the vehicle when the tower is in the upright position for deployment of the platform section. Accordingly, the tower cannot be laterally adjusted to bring it closer to the bridge and, if such adjustment is absolutely necessary, the vehicle must be repositioned to extend further from the edge of the bridge and further into the road making passing by traveling motor vehicles more hazardous.
A conventional under bridge access apparatus that has met with commercial success and that has solved this problem of lateral adjustment of the tower relative to the vehicular chassis is disclosed by U.S. Pat. No. 5,253,731 to Alfons Moog. Specifically, this particular apparatus utilizes pairs of arms (11,12) to form an adjustable parallelogram for shifting the tower relative to the vehicle (3) and bridge (1). Unfortunately, a significant drawback to this design is that the catwalk, by which a worker accesses the tower (8), necessarily changes pitch between a relatively steep incline and steep decline each time the tower is adjusted, resulting in safety concerns for workers who must cross the catwalk.
The present invention addresses the problem of adjusting the tower relative to the vehicular chassis in the aforementioned apparatus sold by Hydra Platforms MFG., Inc., while avoiding the safety concerns presented by the parallelogram design of the Moog apparatus.
Briefly summarized, the present invention includes an under bridge access apparatus in which a cross-linking member connects a tower with a vehicular chassis.
In particular, the present invention includes a tower, a vehicular chassis including a base mounted thereon in movable disposition relative thereto, and a cross-linking member including a pair of elongate arms pivotally joined intermediate respective lengths thereof and extending between and connecting together the tower and the base.
In features of the present invention, the tower includes a ladder section and a platform section connected to the ladder section in movable disposition between a first position, in which the platform section and the ladder section are generally parallel, and a second position, in which the platform section and the ladder section are generally orthogonal. The base itself includes a turntable mounted on the vehicular chassis for rotation about a vertical axis thereof relative to the vehicular chassis, and a tiltable frame mounted on the turntable that pivots relative to the vehicular chassis through an angle of approximately ninety degrees.
In another feature of the present invention, the apparatus includes a catwalk that extends between the base and the tower.
In a preferred embodiment of the present invention, each arm of the cross-linking member includes an end that is slidably mounted on the ladder section of the tower with one of the ends further being fixedly mounted to an exterior of an extendable actuator mounted to the ladder section. Additionally, one of these arms includes an end that is slidably mounted on the tiltable frame and the other arm includes an end that is mounted at a fixed location on the tiltable frame. A first cylinder is connected to the tiltable frame and to the cross-linking member such that the tower moves between a retracted position and an extended position relative to the tiltable frame by extension and retraction of the first cylinder. A second cylinder is connected to the ladder section whereby the ladder section slidably moves between upper and lower positions relative to the ends of the arms of the cross-linking member mounted on the tower by extension of the second cylinder. Also in this preferred embodiment, the catwalk includes a first walkway mounted in fixed disposition against movement relative to the tiltable frame and a second walkway mounted to the end of the second arm slidably mounted to the ladder section, whereby the first walkway and the second walkway move linearly relative to each other during lateral adjustment of the tower relative to the vehicular chassis.